Thai police were searching for a British national Muay Thai fighter suspected of fatally stabbing a US citizen at a tourist resort, dpa reported.
Phuket police named Lee Aldhouse, 28, as the prime suspect in the killing of Dashawn Longfellow, 23, at dawn Saturday, the Phuket Gazette reported.
Longfellow, a US Marine who had served in Afghanistan, was in Thailand as a tourist, studying Muay Thai in Phuket, 600 kilometres south of Bangkok.
The two men got into a fight, Thai boxing style, at a bar early Saturday, according to Longfellow's girlfriend.
"According to witnesses, Mr Longfellow got the best of his opponent in the brawl before it was broken up by bar patrons and staff," the Phuket Gazette reported.
Aldhouse, who last year challenged the island's Muay Thai champion to a bout but pulled out at the last minute due to an injury, allegedly followed Longfellow to his hotel and stabbed him fatally in the chest about dawn, according to the woman.
Longfellow was dead when the ambulance and police arrived.